The present invention generally relates to systems, devices and methods for a medical treatment known as deep brain stimulation (DBS). More particularly, the present invention relates to a miniature implantable DBS device capable of being entirely implanted within the brain and optionally the surrounding tissue.
DBS methods are used to stimulate the brain with electrical impulses to treat a variety of brain conditions and diseases, including but not limited to depression, Parkinson, stroke, essential tremor, dystonia, and tremor due to multiple sclerosis. DBS involves surgically implanting electrodes within the brain and then operating the electrodes to deliver electrical impulses capable of blocking certain activities in the brain, and particularly abnormal activity believed to cause undesirable conditions and symptoms. Programming of the deep brain stimulation treatment is easy and painless, and can offer patients relief from tremors, rigidity, slowness of movement, and stiffness, and may treat balance problems associated with their conditions. The level and duration of stimulation can be adjusted as a patient's condition changes over time.
DBS devices typically comprise a very thin insulated wire lead terminated with four electrode contacts. The lead is routed out of the skull through a small opening and connected to an extension wire subcutaneously routed along the head, neck, and shoulder to an impulse generator or other suitable neurostimulator device implanted under the skin, for example, in the chest area. As such, conventional DBS procedures and devices require two surgical procedures: a surgical procedure to implant the electrodes within the brain, and a second surgical procedure to implant the neurostimulator device in the chest.
The success of DBS is directly related to finding the specific area in the brain for stimulation. Consequently, during the brain surgery portion of the procedure the patient is only given a local anesthetic to numb the area to be operated on, and the patient remains awake and alert so that the surgeon can talk to the patient to ensure the proper areas of the brain are identified for stimulation. While the patient's head is immobilized with a special frame, two holes are drilled in the skull and, guided by imaging techniques, the surgeon implants electrodes to precisely targeted areas on each side of the brain. A neurologist and a neurosurgeon usually decide whether to target one of two areas commonly stimulated by DBS: either the subthalamic nucleus (STN) or the internal globus pallidus (GPi). These structures are deep within the brain and involved in motor control, and stimulation of these areas appears to block the signals that cause the disabling motor symptoms of the disease.
After the electrodes have been properly placed, the second surgical procedure is performed by which the surgeon implants the neurostimulator in the patient's chest, and the extension wire is routed beneath the patient's skin and connected to the electrode leads and the neurostimulator. Depending on the type of neurostimulator selected, two neurostimulators may be implanted to control symptoms affecting both sides of the body. Implantation of the neurostimulator is usually performed while the patient is under general anesthesia. Deep brain stimulation patients are often in the hospital for several days, and stimulation is usually initiated for the first time within a few weeks after implantation. The neurostimulator, which is usually battery powered, is programmed from outside the body to deliver a prescribed and usually continuous dosage of electrical impulses customized to the individual.
Because deep brain stimulation involves brain surgery, it can be appreciated that DBS procedures entail certain risks. The neurostimulator can also pose undesirable risks and side effects, due in part to the size of the neurostimulator. For example, an existing commercial unit used to control Parkinson's disease symptoms is about 7.5 cm wide and 1.3 cm thick, and contains a small battery and computer chip. Finally, there can be inconveniences associated with deep brain stimulation, including battery replacement and hardware malfunctions.